An Introduction to Rainforests

 An Introduction to Rainforests

1 of 4 in our Rainforest Series

What is a Rainforest?

A rainforest consists of a diverse community of flora and fauna that reside amongst trees with a tall canopy, in an environment that sees more than 80 inches of rainfall per year. A rainforest is as much of its own ecosystem as the ocean. They are characterized as having four distinct layers: Emergent, Canopy, Understory and Forest Floor. Rainforests can exist not only in the tropical environment, but also in the temperate climates of the Pacific Northwest region of The United States.

The Layers of the Rainforest

The structure of a rainforest is made up of four distinct layers. Each layer contains plants that contain similar characteristics, especially those that determine what resources are used to promote life.

The Emergent Layer

The layer at the very top of the rainforest is called the Emergent Layer because this is where the tallest vegetation emerges above the upper canopy. In the tropical rainforests in South America, the Brazil Nut Tree can tower above the rest of the forest, reaching heights of 160 feet! High above the rest of the rainforest, the nuts ripen and fall to the ground. Once fallen, these nuts provide sustenance for the fauna that live in their shadows. The Kapok Tree is another resident of the sky high space. Instead of providing food to drop, this tree is beneficial to smaller climbing fauna that depend on sunlight to grow. They can use the Kapok Tree as a willing host to reach the small amount of light coming through the canopy.

The Canopy

Immediately below the Emergent layer is the Canopy. The sunlight available is less than that of the Emergent Layer, and the plants that make up the Canopy will absorb as much of it as they can. Medium height tree tops aren’t the only fauna that thrive in this layer. Varieties of orchids, climbing ferns, vines and “creepers” make up the tightly woven canopy anywhere from sixty to ninety feet from the floor of the forest. This layer contains the most life within the four layers, as it absorbs nearly three quarters of the light coming through the Emergent Layer.

Understory

The Understory is much less dense than either of the layers above it. The amount of light that is available to be absorbed in the Understory is less than twenty percent than what it would be at the Emergent Layer. Budding plants can of all kinds often be seen in the Understory, attempting to start life. However, very few of these will reach maturity. The flora in the uppermost layers will drop their seeds, and they may have enough nutrients to begin life. Once they need more light to survive, they will often die off, leaving decaying matter to accumulate on the Forest Floor.

Forest Floor

The Forest Floor is not covered with life, as you might expect. This is the darkest part of the rainforest. Debris collects here from the plants and animals above. Many animals will live their entire lives never touching the ground. Once they perish, they fall to the forest floor to contribute to new life and new growth. In some areas where enough light penetrates the top three layers of the rainforest, small trees and shrubs can grow. Here, you can find trees whose growth has been stunted by lack of sunlight. Many non-climbing ferns can be found where a stream of light happens to pierce through the thick Canopy and Understory Layers.

Where are the Rainforests?

When we think of a Rainforest, often what comes to mind is a Tropical Rainforest. However, there are more places on Earth in which Rainforests can be found than just the Tropics. Did you know that there are rainforests in Alaska? Most people wouldn’t assume they could find a rainforest that close to the Arctic; but there are actually two within the state of Alaska. Rainforests are categorized as much by the amount of rainfall they receive per year. Any amount over 75-80 inches of rain in a year can put a forest in the running for the title of Rainforest.

The Tropical Rainforests

To be considered a Tropical Rainforest, it must meet criteria beyond the annual rainfall. This biome also holds characteristics such as high average temperatures, nutrient-poor soil, and high levels of biodiversity. Essentially, much of the year these forests are wet and warm.

Central and South America

In Central America, the rainforests cover ground in various countries. The equator runs through this area of the globe, and the Central American rainforests are all located within 25 degrees north and south of the equator. The temperature rarely goes below 70 degrees, no matter what time of the year it is. Look for rainforests in the countries of Belize, Costa Rica, El Salvador, Guatemala, Honduras, Nicaragua and Panama near the equator.

South America boasts arguably the most famous rainforest in the world; The Amazon Rainforest. This massive ecoregion covers nine countries! The majority of The Amazon is located in Brazil. Peru holds just over ten percent of the forest, and Columbia just about ten percent. Within the continent, the six other countries that can claim a small part of The Amazon are: Bolivia, Ecuador, French Guiana, Guyana, Suriname and Venezuela.

Africa

African rainforests are some of the most endangered in the world. Agriculture has taken a lot of the land that once held the precious resource. Over three quarters of the rainforests in the western part of the continent have been completely razed by logging, or to provide land for farmers to use for crops and livestock grazing. 

What is left of the rainforests of Africa are concentrated mostly in the center of the continent. The World Wildlife Fund and the United Nations are putting in place global initiatives to protect the remaining rainforests.

In Madagascar, an island off the east coast of Africa in the Indian Ocean, the rainforests are generally located on the eastern coast. This thin band is made up of six different national parks. UNESCO made this area, “The Rainforests of the Atsinanana,” a World Heritage Site in 2007. Atsinanana is the region in Madagascar in which these rainforests reside.

Southeast Asia

This area of the world is known for its jungles and warm, wet weather. It’s no surprise that more than a few of the countries contain some amount of rainforest. The rainforests that have not been depleted are mostly concentrated in the countries of Indonesia, Malaysia and Papua New Guinea. 

The Cardamom Mountains of Cambodia are in the southwestern region of the country. The rainforest in this area has been a refuge for not just the flora and fauna of the biome, but humans as well. Due to the unstable nature of government over the last few decades, many people have occupied this rainforest, and left parts of it in a state of despair.

National Parks in Southeast Asian countries have been created in part to protect the rainforests. Malaysia has Taman Negara National Park; in which logging is prohibited. Ba Be National Park in Vietnam sits in the northeast section of the country. In the 1930s, Yala National Park was designated in Sri Lanka. Only two sections of Yala National Park are open to the public, and it remains a wildlife sanctuary and 500 square miles of protected land.

Temperate Rainforests of North America

The main difference between the Tropical Rainforests at the equator and the Temperate Rainforests of North America is the overall temperature. These rainforests still have “poor” soil quality (due to the thick canopy cover), high rainfall and a large amount of diversity among the flora and fauna.

Washington State

One of the National Parks that sits within the State of Washington is Olympic National Park. This park holds the distinction of having one of the most famous North American Rainforests, The Hoh Rainforest. The Sitka Spruce, named after a community in Alaska, is protected in the National Park from being exploited for its soft, flexible wood. These towering conifers can reach heights of over 300 feet, providing a dense cover to the ground below them. Up to fourteen feet of rainfall can fall in any given year. Ferns, in particular, love to grow on the dampened trunks of these trees and other evergreen vegetation.

Alaska

Yes, there is a rainforest in Alaska; and not just one! The Tongass National Forest and The Chugach National Forest are both rainforests. Chugach, only 500 miles south of the Arctic Circle, is much smaller than Tongass, but both play a valuable role in climate solution. Sitka Spruce reign here, as they do in the evergreen rainforests in the lower forty-eight states. These old-growth forests provide homes for some of the most recognizable wildlife in North America. Grizzly Bears, Moose, Sockeye Salmon and River Otters use the available natural resources to survive. While logging does still occur in these northern rainforests, The Wilderness Society has made strides to protect the remaining forests from over use by the harvesters of timber.

The Threats to the Rainforests

There is no shortage of things that are actively destroying the rainforests of Earth. Most notably, we as humans are the largest threat. As the population increases, people need places to go. Cities are overflowing in Central and South America in particular, sending hordes of people into the rural areas in the rainforests.

The wood of the trees that make up rainforests is highly sought after for the various reasons. Logging, both legal and illegal, is destroying the rainforests all over the world. Rainforests are made up of old-growth trees that can take decades or more to reach their maturity. Depletion of hardwood tropical trees is not easily, or quickly remedied by replanting.

As the human population grows, another problem arises when a society tries to properly feed everyone. Agriculture is still the main source of food for many people on this planet. Farmers need more and more space to graze their livestock, cattle primarily. Cattle grazing requires vast plots of land with little to no tree cover in order to grow nutrient-rich grass. In tandem with the logging industry, agricultural deforestation is cutting into the edges of the rainforests worldwide.

Knowledge is power, but timber can create power. Unfortunately, providing electricity to the growing population requires fuel. Some power plants cut the trees from unprotected areas in order to burn. Creating electricity this way is still cheaper than cleaner options in much of the world. This makes the use of unprotected land a valuable opportunity for the power industry.

Coming up: The Flora and Fauna of the Rainforests

This is the first edition of our Rainforest Series. Exclusive Enviro would like to share the value we see in our planet’s rainforests with you over the next few months. Check back on the first Wednesday of June to learn more about the residents of Earth’s rainforests!